In 1986, an amnesty law gave legal status and a path to citizenship to unauthorized residents. Today's mass legalization would occur in a much different economic and demographic climate.

Juan Manuel Niebla arrived in Los Angeles in 1976 with a dollar in his pocket.… (Mel Melcon, Los Angeles…)

In 1986, lawmakers decided the problem of illegal immigration had to be dealt with. More than 3 million people were living in the United States after crossing the border illegally or overstaying their visas.

A new law signed by President Ronald Reagan gave legal status and a path to citizenship to most of those unauthorized residents — helping many secure a slice of the American dream but also giving fuel to critics who sought to turn "amnesty" into a pejorative.

Less than 30 years later, the number of immigrants living in the country illegally is thought to have nearly quadrupled, and the freighted baggage of amnesty looms over new efforts to reform the nation's immigration laws.

With four times as many people potentially eligible, today's mass legalization would occur on a much larger scale. The specifics of the current proposal are different, the global economy is different, and the immigrants themselves are different, hailing from South Korea as well as Mexico and fanning out from traditional enclaves like Los Angeles to populate small towns across America.

Still, the reams of post-1986 studies offer an indication of what might happen if millions of immigrants receive legal status. And there is broad agreement on one thing: The flow of illegal immigration must somehow be stanched, so there is never a need for an amnesty again. In that respect, 1986 was an utter failure.

"The goal's got to be that people come with visas, not with smugglers, that they come for jobs that we need people to come fill," said Angela Maria Kelley, an immigration policy expert with the pro-reform Center for American Progress.

The 855-page Senate bill, currently in committee, contains a path to citizenship taking at least 13 years, with provisional status to be granted almost immediately to those who were in the country before 2012. Proponents avoid calling it amnesty, even as they tout the moral imperative of bringing 11 million people out of the shadows. Opponents wield the word as a weapon, decrying amnesty as a free pass to lawbreakers that should not have been doled out in 1986, nor again in 2013.

Both camps trot out economic projections. Higher immigrant wages will pad tax coffers and boost the domestic product by billions of dollars, one argument goes. Opponents predict a drain on public funds as newly legalized immigrants apply for government benefits, and harm to American workers as immigrants get better jobs.

"After legalization, they'll be eligible for virtually every job in the country," said Ira Mehlman, a spokesman for the anti-legalization Federation for American Immigration Reform. "People whose jobs are not threatened right now will find themselves in competition with these workers."

Juan Manuel Niebla arrived in Los Angeles in 1976 with a third-grade education and a dollar in his pocket. He found a job at a factory, where his salary was many times the $5 a day he made as a construction worker in Mexico. He raised a family, learned English and bought a house, all while living in the country illegally.

For Niebla, the 1986 amnesty meant freedom from fear. He no longer had to worry about being deported if he was pulled over while driving to work. He was finally able to visit his parents in Mexico.

Initially, he stayed at the same job, working his way up from machine operator to supervisor. Then, his boss ordered him to accept a pay cut or be laid off. Niebla chose the latter, knowing that as a U.S. citizen, he could tide himself over with unemployment benefits. He immediately found work as a landscaper with the city of Los Angeles, where he now makes $24 an hour and looks forward to a pension when he retires.

"This country is for everybody, especially if they're hardworking, honest people," said Niebla, 63, of Highland Park. "I have everything — good health, a good job."

James P. Smith, a labor market expert at Rand Corp., believes that legalizing the 11 million unauthorized immigrants — 1 in 4 of whom live in California — is the right thing to do.

But unless the new legislation succeeds in stopping illegal immigration through a combination of more work visas, border security and workplace enforcement, the cycle may repeat. A new generation of illegal border crossers and over-stayers may find inspiration in stories like Niebla's.

"The very fact that it was successful in that way was a signal that this will happen again, that this is the American solution to the immigration problem, legalizing those who are here and dealing with it again 15, 20 years in the future," Smith said of the 1986 amnesty.

Many studies have found that wages increased for amnesty recipients as a group — as much as 15% in the first five years, according to the U.S. Department of Labor. If immigrants earn more, they will spend more and pay more taxes, potentially creating more jobs.